1. Field of the Invention
This invention relates to pipeline inspection tools, and more particularly to apparatus and methods for data collection on an in-line inspection tool.
2. Background of the Invention
Oil, petroleum products, natural gas, hazardous liquids, water, and the like are often transported using pipelines. The majority of these pipelines are constructed from steel pipe. Once installed, a pipeline will inevitably corrode or otherwise degrade. Proper pipeline management requires identification, monitoring, and repair of defects and vulnerabilities of the pipeline. For example, information collected about the condition of a pipeline may be used to determine safe operating pressures, facilitate repair, schedule replacement, and the like.
Typical defects of a pipeline may include corrosion, gouges, dents, cracks, and the like. Corrosion may cause pitting, general wall loss, or cracking, thereby lowering the maximum operating pressure of the pipeline. Vulnerabilities may also include combined stress and chemical or biological action such as stress corrosion cracking. Without detection and preemptive action, all such defects and vulnerabilities may lead to pipeline failure.
Information on the condition of a pipeline is often collected using an in-line inspection (ILI) tool. Ferromagnetic pipelines can be inspected for defects, including cracks extending along the axis of a pipe, by a limited number of technologies. These technologies include magnetic flux leakage (MFL) inspection, ultrasonic (UT) inspection, eddy current inspection, and, in certain applications, inspection using electromagnetic acoustic transducers (EMATs).
EMAT inspection has failed to gain widespread use on in-line inspection tools. This failure has largely been the result of an inability to separate meaningful signal from the surrounding noise. Moreover, problems have arisen from the complex geometries involved. For example, building on the disclosures of Bobrov et al. (U.S. Pat. No. 4,100,809), Alers et al. (U.S. Publication No. 20090078048) disclose a device that projects a transverse shear, ultrasonic, guided wave, that wave is oriented at an angle of ten degrees to sixty degrees from the axis of the pipeline. However, when the wave strikes an axially oriented defect (e.g., an axially oriented crack), it does so at an oblique angle and is, consequently, reflected away from the transmitter at a mirror image angle. Thus, the proper location for a corresponding receiver cannot be determined with specificity, as it depends on the location of the defect with respect to the transmitter.
While some technologies are more adversely affected by the foregoing factors than are others, all such techniques may be improved with better signal detection, recognition, and geometries. What is needed is a better device and method for the generation and reception of pulsed signals for the various inspection technologies.